In the steel-making industry, refractory products, such as nozzles, liners, and the like, are subjected to severe thermal shock when molten metal first comes in contact with the surface of the refractory product. In addition to this thermal shock, molten metal, slag, and other impurities flowing over the surface of the refractory tends to abrade such surface. Consequently, it is desirable for the refractory component to have a high thermal shock resistance as well as a high resistance to corrosion and wear.
Rebonded fused silica products have seen wide use in such applications, i.e. where high thermal shock resistance and wear resistance are main requirements. Such products are typically formed of fused silica particles by means of a casting process. In this respect, the silica particles are mixed with water to form a slurry (conventionally referred to as a "slip") which may be cast in plaster molds having the shape of the components to be formed. A characteristic of products formed in this manner is an inherent porosity which while enhancing the product's thermal shock resistant properties reduces it corrosion and wear resistance. The porosity of such products is affected by the size of the particle used, as well as the amount of moisture contained in the silica slip. More specifically, because moisture is necessary to form the silica slip, porosity inevitably exists in every cast product as a result of the evacuation of the moisture during the casting process. With respect to the particle size, generally, the larger the particle used in forming the product, the greater the porosity of the resulting product and, in turn, the lower the corrosion resistance. Consequently, most products formed heretofore were generally formed from silica particles having grain size less than a millimeter, and these products generally exhibited a 10% or more porosity and a density of approximately 1.90-1.95 grams per cubic centimeter, which characteristics resulted from the particle size and moisture content of the casting material.
The present invention provides a refractory product having a relatively high density and low porosity which has improved thermal shock resistance, as well as improved resistance to corrosion and/or erosion.